The present invention relates to method and device for selecting a starting gear in a vehicle.
The present invention also relates to a computer program, a computer program product and a storage medium, such as a computer memory, all to be used with a computer for executing said method.
The selection of a starting gear in a heavy vehicle can be selected in dependence of vehicle weight and road inclination. The criteria is that the vehicle have a good ability to take off and that heat energy released when, for example lamellas in a friction clutch arranged between a propulsion unit and a gearbox is slipping during the take off, has to be limited. A great amount of released heat energy in the clutch during a take off results in a high clutch temperature and increased clutch wear.
WO0242108 and U.S. Pat. No. 6,412,361 disclose examples of arrangements for starting gear selection.
When different take-offs sometimes occur relatively close to each other in time, for example when driving in a queue, then a too high starting gear tends to be selected. There is a risk that the clutch will be overheated. On the other hand an even higher starting gear could have been selected when few vehicle take-offs occur, for example in long-distance traveling, where there is relatively long between the take-offs.
The state of the art solution is usually a compromise between the long-distance traffic condition and the queue driving condition.
A technical problem addressed by an aspect of the present invention is therefore to provide a starting gear selection with increased adaptability. Moreover, the present invention seeks, according to an aspect thereof, to provide such a starting gear selection that is better suited, for example, to the requirements of heavy commercial vehicles.
It is desirable to provide a starting gear selection with improved adaptability which is capable of enhancing clutch endurance for a vehicle that has to, at least at times, perform frequent take-offs and at the same time enhancing the ability for take off for a vehicle that during at least a period goes long-distance.
According to a first aspect of the invention, a method comprises the steps of:                measuring at least one starting gear selection parameter;        selecting a starting gear for the next coming vehicle take-off in dependence of said measured starting gear selection parameter. The method is characterized in that said starting gear selection parameter is the number of vehicle take offs per time unit.        
In one embodiment of the method according to an aspect of the invention said starting gear selection parameter can be two parameters, where the first is said number of starts per time unit and the second parameter is one of:                acceleration in movement of an accelerator pedal being depressed by a driver of the vehicle during at least one preceding vehicle take-off,        accelerator pedal position of said accelerator pedal during at least one preceding vehicle take-off and/or,        measured wear of a clutch arranged for torque transmission between a propulsion unit and a gearbox in said vehicle.        
In one embodiment of the method according to an aspect of the invention said starting gear selection parameter can be three parameters, where the first parameter is said number of starts per time unit and the second and third parameter is two of said:                acceleration in movement of an accelerator pedal being depressed by a driver of the vehicle during at least one preceding vehicle take-off,        accelerator pedal position of said accelerator pedal during at least one preceding vehicle take-off and/or,        measured wear of a clutch arranged for torque transmission between a propulsion unit and a gearbox in said vehicle.        
In one embodiment of the method according to the invention said starting gear selection parameter can be all said four parameters.
In a further embodiment of the method according to an aspect of the invention the driver manually selects and engages said starting gear for the next coming vehicle take-off after being advised by a starting gear selection advisor, which advises in dependence of said one or two starting gear selection parameters.
In another embodiment of the method according to an aspect of the invention said starting gear for the next coming vehicle take-off is automatically selected and engaged in dependence of said one or two starting gear selection parameters.
According to an aspect of the invention, there is provided a vehicle transmission comprising a clutch, a gearbox and a control unit with sensors arranged for measuring at least one starting gear selection parameter, and where a propulsion unit is drivingly connected to driven wheels of a vehicle via said clutch and said gearbox, characterized in that said control unit is arranged to performed the steps of the method noted above.